Eeek, I see oil in the coolant reservoir of my W12 Touareg.
As far as I can tell, engine temps were stable and normal prior to this sudden occurrence. Based on this, my top suspect is not the head gasket, but the oil-cooler, which is a coolant/oil heat exchanger.
This is not a cheap part, and I expect the dealer to charge a handsome fee for labor, so I'd like to be sure that it is indeed the oil cooler and not something more invasive like a head gasket (shudder).
Here is a diagram of the oil circulation system on the W12
Is there a way for me to diagnose the leak, preferably with the oil cooler in situ?
(I feel like I'm clutching at straws with the "in situ" part of the request)
A lot of YouTubers like to submerge the cooler in water and use compressed air to look for bubbles, but this obviously involves unbolting the oil cooler from its home in the engine bay.
If extraction is the only option, I can understand that - just that I'm not looking forward to the ordeal.